David Cameron faces fresh calls to scrap the Bedroom Tax after damning new research showed it is plunging hundreds of thousands of families into debt.

About half-of those clobbered by the penalty were unable to pay their rent in the first three months after it came in, the study found.

And one in four were in rent arrears for the first time, according to the National Housing Federation (NHF) survey.

With 660,000 families affected across the country that means more than 330,000 will have fallen behind with their rent.

That includes about 165,000 who always paid their rent on time in the past.

The shocking conclusions fuelled demands of for the Bedroom Tax to be axed.

The United Nations has already called for the policy to be scrapped.

And NHF chief David Orr said: “What more proof do you need that the Bedroom Tax is an unfair, ill-planned disaster that is hurting out poorest families?

"There is no other option but to repeal.”

Labour’s Liam Byrne added: “The jury is now in.

Hated tax: Labour's Liam Byrne

"David Cameron’s hated Bedroom Tax is pushing a generation into foodbanks and loan-sharks.”

Social housing tenants with a spare bedroom are having to pay an average of £14 a week more in rent after having their housing benefit slashed.

Those with two spare rooms lost 25% under the policy introduced in April.

Ministers claim that it will help with the housing crisis by encouraging people with spare rooms to move, freeing up larger family homes.

But many victims of the Bedroom Tax have nowhere to move.

The National Housing Federation estimates that although there are 180,000 under-occupied two bed social homes just 85,000 one bed properties became available for them to move into in 2011-12.

A NHF survey of 51 housing associations found that 32,432 families out of 63,758 they home who have been hit by the tax went in to rent arrears between the start of April and the end of June.

A separate study of 38 associations found that 11,064 out of the 43,989 households affected owed rent for the first time.

Chief Executive David Orr said: “This is the most damning evidence yet to show that the bedroom tax is pushing thousands of families into a spiralling cycle of debt.

“If these figures are replicated nationwide, over 330,000 households could already be struggling to pay their rent and facing a frightening and uncertain future.

“What’s more, people can’t even move to smaller homes to avoid the bedroom tax because there aren’t enough smaller properties out there.

“Housing associations are working flat-out to help their tenants cope with the changes, but they can’t magic one-bedroom houses out of thin air.

"People are trapped.”

Sovereign Housing Association, which took part in the NHS study, has 2,360 households affected by the Bedroom Tax and the majority are now in arrears.

Chief executive Ann Santry said: “With huge demand for affordable homes we recognise the need to maximise the use of every room and so we’re investing heavily in supporting our residents to adapt to the changes wherever possible.

“However, six months in, we are seeing the most vulnerable families, couples or individuals on the lowest incomes beginning to struggle.”

The Bedroom Tax will save just £500million, according to official figures.

That is less than the coalition plan sot spend extending free school meals to all infant school pupils.

Critics argue that it could actually end up costing money as people are driven out of social housing and into the more expensive private rental sector.

But a Department for Work and Pensions spokesman said: “The removal of the spare room subsidy is a necessary reform to return fairness to housing benefit.

“Even after the reform we pay over 80% of most claimants’ housing benefit - but the taxpayer can no longer afford to pay for people to live in properties larger than they need.

"It is right that people contribute to these costs, just as private renters do.

“It is just wrong to suggest the early stages of the policy - as people start to adjust to the changes - represent long-term trends in any way whatsoever or that a self-selecting poll of a small minority of landlords provides a clear picture of the reform.”

The Government has made available £190 million of extra funds to support vulnerable tenants as the policy takes effect and is monitoring its use, the spokesman added.